The present applicant proposed a radiator for a liquid cooling type cooling device for cooling a power device (semiconductor element), such as, e.g., an IGBT (Insulated Gate Bipolar Transistor), used for a power conversion device to be mounted on, for example, an electric vehicle, a hybrid vehicle, a train, etc. (see Patent Document 1). The liquid cooling type cooling device is provided with a casing having a top wall, a bottom wall, and a peripheral wall. In the casing, a coolant passage in which a coolant flowed into the casing flows is provided. A heating element is attached to at least either one of the top wall outer surface and the bottom wall outer surface of the casing. In the liquid cooling type cooling device configured to cool the heating element by the coolant flowing through the coolant passage, a radiator which is arranged in the coolant passage in the casing radiates the heat emitted from the heating element to the coolant. The radiator is composed of a plurality of vertically elongated rectangular shaped fin plates arranged in parallel at intervals, and rod-shaped connecting members extending in a direction intersecting with the longitudinal direction of the fin plate and integrally connecting all the fin plates. All the fin plates are arranged at intervals in a thickness direction in a state in which the longitudinal direction of the fin plate is oriented in the flow direction of the coolant and the width direction of the fin plate is oriented in the vertical direction. At least one notch is formed in one side edge portion out of both side edge portions of the fin plate in the width direction. At least one notch is formed in the other side edge portion out of both side edge portions of the fin plate in the width direction at a position deviated from the notch of one side edge portion in the longitudinal direction of the fin plate. Connecting members are press-fitted into the notches of both side edge portions of all the fin plates so as not to protrude from the notches. Thus, all the fin plates are integrally connected by the connecting members.
In the case of the radiator described in Patent Document 1, however, since a rod-shaped connecting member is required, the number of parts increases.
The radiator described in Patent Document 1 is produced by the method including a first step, a second step, a third step, and a fourth step, which will be described below. The first step is a step of subjecting a metal blank plate to press working to punch out the metal blank plate to obtain a plurality of vertically elongated rectangular shaped fin plates having notches formed respectively in a portion close to the one end of one side edge portion in the width direction and a portion close to the other end of the other side edge portion in the width direction so that the longitudinal direction is oriented in the width direction of the metal blank plate and the width direction is oriented in the longitudinal direction of the metal blank plate in a half-punched state in which both end portions in the longitudinal direction are connected to the bridge portions via the connecting portions. A second step is a step of bending a portion of the bridge portion between adjacent fin plates into a substantially S-shape so as to orient the width direction of each of all the fin plates in the vertical direction. A third step is a step of press-fitting connecting members into notches formed in the longitudinal one end of one side edge portion of each of all the fin plates in the width direction and notches formed in the longitudinal other end of the other side edge portion of each of all the fin plates in the width direction. A fourth step is a step of separating all the fin plates from the bridge portions by cutting all the connecting portions which connect the fin plates to the bridge portion. Since the method requires the above-described four steps, the work is troublesome. Moreover, in the fourth step, all the connecting portions connecting the fin plates to the bridge portions are cut to separate all the fin plates from the bridge portions, so that the bridge portions are discarded. Therefore, the material yield is deteriorated. As a result, the production cost of the radiator increases.